1. Field of the Invention
This invention pertains to printing presses, and in particular to a rotary press of the type wherein a plate cylinder carries two printing plates in side-by-side arrangement. Still more particularly, the invention is directed to improved means for adjusting the positions of the printing plates in both axial and circumferential directions of the plate cylinder, as for the precise registration of various color impressions in color printing.
2. Description of the Prior Art
The side-by-side arrangement of two printing plates on a single plate cylinder has been resorted to extensively, as in the case where the plant is not equipped to manufacture printing plates large enough to singly cover the plate cylinder, or where such large plates, if manufactured at all, would be inconvenient or difficult to handle. Usually, the two printing plates are fastened to the plate cylinder at points angularly displaced from each other, so that the fastening points may not be simultaneously subjected to pressure in printing.
In the case of multiple-color printing, for example, the exact positioning of the printing plates on several plate cylinders is necessary for proper registration of the colored impressions on paper or other surface. Such exact positioning of the printing plates is difficult to attain, however, because of the manufacturing errors of the printing plates and of the means for fastening same to the plate cylinders.
Some prior art multiple-color rotary presses are equipped with means for adjusting the position of one of the printing plates on each plate cylinder, but manual readjustment is usually necessary for the other printing plate. Such adjustment of the printing plate positions according to the prior art involves a highly troublesome and time-consuming procedure, imposing prolonged downtime upon the press.